Contact type micro piezoresistive shear-stress sensor

Abstract

There is disclosed a semiconductor sensor for measuring the contact shear stress distribution between the socket of an above-knee (AK) prostheses and the soft tissue of an amputee's stump. The sensor is fabricated by the micro-electro-mechanical system (MEMS) technology, and its main sensing part is 2-X shaped with a flange structure. The sensor is prepared by anisotropic wet etching of bulk silicon in KOH solution and a square flange above the sensing diaphragm is formed through surface micromachining of deposited SiO 2 thin film. This invention has the following characteristics: piezo-resistivity of the monolithic silicon will be utilized to convert shear deformation of the sensor into an electrical signal and a micro sensor which can measure the shear force vector acting on the sensing flange.

1. A contact-type micro piezoresistive shear-stress sensor comprising:
 a) a silicon substrate;  
 b) a sensing diaphragm formed into etched cavities at preset locations on the silicon substrate and having a substantially square shape;  
 c) a flange framed by means of etching technology at the center of said sensing diaphragm;  
 d) two X-shaped piezoresistors implanted at the center of adjacent longitudinal sides of said sensing diaphragm between the respective side and the center of said sensing diaphragm; and  
 e) a protective membrane of semi-conductor protective material formed on said sensing diaphragm.  
 
   
   
     2. The contact-type micro piezoresistive sheer-stress sensor as defined in  claim 1 , wherein said flange is formed of the same material as said protective membrane. 
   
   
     3. The contact-type micro piezoresistive sheer-stress sensor as defined in  claim 2 , wherein said protective membrane and said flange are formed of SiO 2  or Si 3 N 4 . 
   
   
     4. The contact-type micro piezoresistive sheer-stress sensor as defined in  claim 1 , wherein said silicon substrate is formed of high doping semi-conductor piezoresistive material. 
   
   
     5. The contact-type micro piezoresistive sheer-stress sensor as defined in  claim 3 , wherein the formation of the flange comprises immersion in an etching agent at a concentration of HF:H 2 O of 1:10, and preparation of the semi-conductor is according to the process of pattern etching for size and shape.